A method of irradiating a sample with light and analyzing the sample using the transmitted light, the reflected light, or the scattered light is widely known as an absorbance measurement method or the like. In these measurement methods, a flow cell including a cell channel serving as a flow path through which a sample flows is used. A transparent window member used for taking light into the cell channel is attached to the flow cell. Here, “transparent” means that the transmittance is high (at least 80% or more) with respect to the wavelength of light used for analysis. Examples of the transparent window member include a flat window formed of synthetic quartz.
In order to efficiently irradiate a sample, flowing through the cell channel in the flow cell, with light, a lens such as a hemispherical lens or a ball lens may be used. In this case, although the lens may be disposed outside a window portion of the flow cell, the lens is used as the window member of the flow cell in order to, for example, reduce the number of parts (see Patent Document 1).
Patent Document 1: Japanese Patent Laid-open Publication No. 2014-55784
Patent Document 2: Japanese Unexamined Patent Publication No. 2012-522253